Table 3.

Variables to consider when designing clinical studies related to immunity in the aged.

	Clinical study considerations
Age	Clearly defined age categories
	Young: 20 to ≤45 years
	Old: >45 to ≤85 years
	Very old/elderly: >85 years
Health status	Frailty: three of the five following characteristics: weight loss, weakened handgrip, exhaustion, reduced gait speed, and reduced activity
	Concentrations of serum inflammatory proteins: IL-6, TNF-α, IL-1β, and C-reactive protein
Sex hormone status	Time of menopause
	Serum concentrations of sex hormones
	Hormone replacement therapy